Cooler inventory management system with light guard

ABSTRACT

An apparatus for tracking the movement of a number of products. The apparatus includes a shelf with the products positioned thereon. The shelf has a fit end with an optical sensor positioned thereabout. The optical sensor tracks the movement of the products. A guard is positioned about the first end of the shelf adjacent to the optical sensor so as to prevent exterior light from interfering with the optical sensor.

This application is a continuation-in-part of 09/329,084 Jun. 9, 1999.

TECHNICAL FIELD

The present invention relates generally to systems and methods fortracking product usage and more specifically relates to systems andmethods for tracking product inventory from a shelf within arefrigerated cooler.

BACKGROUND OF THE INVENTION

Various methods have been employed in the past to track product usage,purchase, or consumption from a dispensing apparatus such as a vendingmachine and the like. Various types of sensors or counters may be usedto keep track of the number of products dispensed from such a machine.For example, each “drop” of a bottle, a can, or other item from avending machine may be tracked. These “smart” vending machines can keepan accurate tally of the amount of product dispensed because the machineis a controlled environment, i.e., the product is not dispensed untilthe selection button is pushed and the sale is completed.

This type of “smart” technology, however, has not been applicable totrack the sale of products merely placed on a store or a cooler shelf.The existing vending machine technology is not directly applicablebecause a consumer is free to pick up a product, inspect it, take it, orreturn it to the shelf and make a different selection, i.e., the shelfis not a controlled environment. For example, a consumer may pick up abottle or can containing a carbonated soft drink off of a shelf and thenreturn that bottle or can and make a different selection. The return ofthe bottle or can may inflate the number of items actually removed fromthe shelf if only the removals are counted or monitored.

What is needed therefore is a system and method for tracking the use,purchase, or consumption of items placed on a shelf. The system andmethod must be able to keep track of removals and additions to theshelf. Further, these systems and methods must be implemented inconsumer friendly and/or otherwise non-obtrusive manner.

SUMMARY OF THE INVENTION

The present invention provides an apparatus for tracking the movement ofa number of products. The apparatus includes a shelf with the productspositioned thereon. The shelf has a first end with an optical sensorpositioned thereabout. The optical sensor tracks the movement of theproducts. A guard is positioned about the first end of the shelfadjacent to the optical sensor so as to prevent exterior light frominterfering with the optical sensor.

Specific embodiments of the present invention provide for the guard toextend across the shelf. The guard also may be in the shape of a wingpositioned adjacent to the optical sensor. The wing may be sized so asto prevent exterior light from interfering with the optical sensor. Theguard may have a number of flanges and an extended lip so as to attachto the shelf in a snap fit. The guard may have a number of panelsthereon. The guard also may have advertising indicia thereon. Theadvertising indicia may be on a label. The guard may be made from athermoplastic such as PETG (Polyethylene Terepthalate Glycol). The guardmay be made out of a substantially opaque material or a translucentmaterial with a covering layer. The covering layer may be asubstantially opaque material.

The optical sensor may have one or more emitters and one or morereceivers. The emitters and receivers may be positioned along a diagonalline. The optical sensor may include a controller so as to track theremoval and the insertion of the products from the shelf. The exteriorlight may be ambient light or a light source positioned within thecooler.

A further embodiment of the present invention provides an apparatus fortracking the movement of a number of products. The apparatus includes ashelf with the products positioned thereon. The apparatus also includesan optical sensor and a guard positioned adjacent thereto. The apparatusalso may include a controller connected to the optical sensor so as totrack the removal and the insertion of the products from the shelf.

A further embodiment of the present invention provides an apparatus fortracking the movement of a number of products. The apparatus includes ashelf with the products positioned thereon. The apparatus also includesan optical sensor to track the movement of the products. The apparatusalso includes a guard positioned adjacent to the optical sensor. Theguard has advertising indicia thereon.

Other objects, features, and advantages of the present invention willbecome apparent upon review of the following detailed description of thepreferred embodiments of the present invention when taken in conjunctionwith the drawings and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic representation of a refrigerated cooler.

FIG. 2A is a perspective view of a multi-channel dispensing slide foruse in the refrigerated cooler.

FIG. 2B is a plan view of the emitters.

FIG. 2C is a plan view of the receivers.

FIG. 3 is a plan view of one channel of the multi-channel dispensingslide.

FIG. 4 is a schematic showing the controller and the optical sensors.

FIG. 5 is a flow chart of the single tray event recognition logic.

FIG. 6 is a flow chart of the signature analysis subroutine.

FIG. 7A is a chart showing the various event states of the presentinvention for a lift event.

FIG. 7B is a chart showing the various event states of the presentinvention for a drop event.

FIG. 8 is a flow chart of a single shelf scan diagram with a signaturetable.

FIG. 9 is a sample spreadsheet layout.

FIG. 10 is a perspective view of the shelf, the products, and the guard.

FIG. 11 is an exploded view of the shelf, the posts, and the guard.

FIG. 12 is a perspective view of the guard.

FIG. 13 is a perspective view of the shelf, the posts, and a number ofwings.

DETAILED DESCRIPTION OF THE INVENTION

Referring now in more detail to the drawings, in which like numeralsrefer to like parts throughout the several views, FIGS. 1-3 show arefrigerated cooler 100 for use with the present invention. Therefrigerated cooler 100 is of conventional design. The cooler 100 mayinclude an insulated shell 110 and an outer door 120. The outer door 120preferably is transparent in whole or in part such that the consumer cansee within the cooler 100. The use of the door 120 is not required. Thecooler 100 generally has a mechanical refrigeration system (not shown)of conventional design. A preferred cooler 100 is manufactured by theBeverage-Air Company of Spartanburg, S.C. under the mark MT-27(“Marketeer”). The shell 110 and/or the door 120 also may have a contactswitch 125 such that a determination can be made whether the door 120 isopen or closed so as to trigger the present invention.

Located within the cooler 100 may be a plurality of shelves 130. Anytype of shelf 130 may be used. The shelves 130 are preferably, but notnecessarily, gravity feed organizers such as the shelves 130 sold underthe mark “Visi-Slide” by Display Technologies of New York, N.Y. Otheralternatives may include the use of neck-tracker shelves that hold abottle by its neck or a horizontal serpentine design.

The shelves 130 each preferably have a plurality of channels 140therein. A plurality of products 150 is placed within each of thechannels 140. Each channel 140 has a first end 160 near the door 120 anda second end 170 near the rear of the cooler 100. The second end 170 isgenerally elevated somewhat from the first end 160. In this fashion, theproducts 150 will slide under the force of gravity towards the first end160 of the channel 140 towards the door 120. The first end 160 of thechannel 140 preferably has a barrier 180 such that the products 150 donot fall out of the channel 140. When a first product 190 is removedfrom the first end 160 of the channel 140, a second product 200 thenslides into place adjacent to the barrier 180 on the first end 160 ofthe channel 140. The channels 140 are preferably made from aluminum,stainless steel, other metals, plastic, vinyl-coated wire, or othertypes of substantially non-corrosive materials or combinations thereof.

The present invention provides for the use of a tracking system 250within the cooler 100. The tracking system 250 includes a plurality ofoptical sensors 260 used in conjunction with a micro-controller 270. Theoptical sensor 260 may be a conventional photoelectric sensor using aninfrared (IR) emitter 280 and one or more receivers 290. Specifically, acombination of Light Emitting Diodes (LEDs) and Light ReceivingPhototransistors (LRPs) may be used. The optical sensors 260 may besupplied by Touch Controls, Inc. of Fallbrook, Calif. Other types ofsensing devices may be used, such as other types of conventionalmechanical, electrical, or optical sensors. The micro-controller 270 maybe a conventional processing unit. Depending upon the number of opticalsensors 260, a conventional multiplex card 275 may be used.

Each channel 140 may have a first post 300 positioned on a first side142 of the channel 140 and a second post 310 positioned on the opposingside or a second side 144 of the channel 140. The posts 300, 310 arepositioned on the first end 160 of the channel 140 near the barrier 180.Positioned on the first post 300 may be a lower emitter 320 and an upperemitter 330. The emitters 320, 330 are spaced from each other and may bepositioned either vertically on top of each other or along a diagonal asis shown in FIG. 2B. The use of the diagonal alignment is useful whenthe product 150 is, for example, in the shape of a contoured bottle. Ifthe emitters 320, 330 are positioned along a substantially verticalline, the contours of the bottle may cause a false reading. Further, afalse reading also may be caused if the emitters 320, 330 are positionedalong the vertical line and the product 150 is tipping or leaning as itmoves. The use of the diagonal alignment therefore is helpful intracking the movement of the product 150. This movement may be the upand down motion as the product 150 is being removed from or placedwithin the channel 140 or the sliding motion as the product 150 slidesalong the channel 140.

Positioned on the second post 310 may be one or more lower receivers 340and one or more upper receivers 350. More than one receiver 290 may beused with each emitter 380. Preferably, two receivers 340, 350 are usedwith each emitter 320, 330. The receivers 340, 350 are positioned on thesecond post 310 in alignment with the emitters 320, 330. The lowerreceivers 340 will receive the IR beam from the lower emitter 320 andthe upper receivers 350 will receive the IR beam from the upper emitter330.

The relative position of the emitters 320, 330 and the receivers 340,350 described herein are by way of example only. For example, oneemitter 320, 330 may be on the first post 300 while another emitter 320,330 may be on the second post 310, or vise versa, with the receivers340, 350 in corresponding locations. The emitters 320, 330 and thereceivers 340, 350 may use a signal filtering method due to the lightingwithin the cooler 100 or due to ambient lighting. A conventional phaselock loop circuit or similar methods may be used to distinguish thebackground lighting from the light transmitted by the emitters 320, 330.

As is shown in FIG. 4, the emitters 320, 330 and the receivers 340, 350create a circuit with the micro-controller 270 and the multiplex card275. The emitters 320, 330 and the receivers 340, 350 are generallypositioned near the barrier 180 such that the first product 190 blocksthe respective beams when the first product 190 is resting against thebarrier 180. The contact switch 125 of the door 120 also may beconnected within the circuit to the micro-controller 270. A hold switchor a reset switch 127 also may be used. The hold switch 127 may preventthe operation of the tracking system 250 during, for example, restockingof the cooler 100 with the product 150.

FIG. 5 shows a flow chart of the event recognition or the “scan” logicfor use in a single channel 140 of a cooler 100. As is shown therein atstep 400, the micro-controller 270 checks the door switch 125 (only if adoor 120 is used), the hold switch 127, and then scans the next productchannel 140. If the door switch 125 indicates that the door 120 to thecooler 100 is closed, there is no need to go any further because aconsumer cannot remove or replace the product 150 if the door 120 isclosed. Likewise, if the hold switch 127 is activated, themicro-controller 270 will not proceed. If the door 120 is open and thehold switch 122 is not activated, the micro-controller 270 will selectthe appropriate channel 140.

At step 410, the micro-controller 270 reads the present state of theoptical sensors 260. The available states include:

(1) the lower emitter 320 and the lower receiver 340 are blocked and theupper emitter 330 and the upper receiver 350 are blocked,

(2) the lower emitter 320 and the lower receiver 340 are open and theupper emitter 330 and the upper receiver 350 are open;

(3) the lower emitter 320 and the lower receiver 340 are blocked and theupper emitter 330 and the upper receiver 350 are open; and

(4) the lower emitter 320 and the lower receiver 340 are open and theupper emitter 330 and the upper receiver 350 are blocked.

At step 420, the micro-controller 270 obtains the previous state of theoptical sensors 260. The possible states of the optical sensors 260 arethe same as those as described above. At step 430, an event signature iscreated containing the current state and the previous state of theoptical sensors 260. At step 440, a signature analysis sub-routine isretrieved. The signature analysis sub-routine is described in detailbelow at FIG. 6. After the signature analysis sub-routine is completed,a determination of whether a valid event has taken place is made at step450. A valid event would be a “lift”, i.e., removing the first product190 or a “drop”, i.e., replacing the first product 190. If a valid eventhas taken place, the micro-controller 270 obtains the cooleridentification number and the current time. The combination of theevent, the cooler identification, and the time stamp forms an eventrecord. In step 470, this event record is stored in RAM 277 or othertype of memory.

FIG. 6 shows the signature analysis sub-routine. At step 500, themicro-controller 270 determines whether or not a change of state hastaken place. If so, at step 510 the micro-controller 270 determineswhether or not the lower emitter 320 and the lower receiver 340 areblocked. If so, the signature analysis sub-routine returns to the scanroutine of FIG. 5. If not, the micro-controller 270 next determineswhether the upper emitter 330 and the upper receiver 350 are blocked atstep 520. If the upper emitter 330 and the upper receiver 350 are open,the micro-controller 270 determines whether the lower emitter 320 andthe lower receiver 340 in the previous state were blocked. If not, themicro-controller 270 returns to the scan routine of FIG. 5. If so, atstep 540 the micro-controller 270 determines whether the lower emitter320 and the lower receiver 340 were blocked in the previous state. Ifso, micro-controller 270 returns to the scan routine of FIG. 5. If not,at step 550, the micro-controller 270 determines that a valid lift eventhas occurred and sets the delay timer within the micro-controller 270.The length of time used by the delay timer is determined such that thelift event can be competed before another scan routine takes place. Themicro-controller 270 then returns to the scan routine of FIG. 5.

If at step 520 the micro-controller 270 determines that the upperemitter 330 and the upper receiver 350 are blocked, the micro-controller270 proceeds to step 560. At step 560, the micro-controller 270determines whether the lower emitter 320 and the lower receiver 340 aswell as the upper emitter 330 and the upper receiver 350 were blocked inthe previous state. If so, the micro-controller 270 returns to the scanroutine of FIG. 5. If not, at step 570 the micro-controller 270determines whether the delay timer is on. If so, the micro-controller270 returns to the scan routine of FIG. 5. If not, at step 580 themicro-controller 270 determines that a valid drop event has taken place.The micro-controller 270 then returns to the scan routine of FIG. 5.

FIGS. 7A and 7B are diagrammatic representations of the changes of stateof the emitters 320, 330 and the receivers 340, 350. In FIG. 7A, a validlift event is shown. The emitters 320, 330 and the receivers 340, 350are both open in the present state 590 while the upper emitter 330 andthe upper receiver 350 are blocked and the lower emitter 320 and thelower receiver 340 are open in the previous state 600. In this case, theoptical sensors 260 determine that the first product 190 was beinglifted out of the channel 140 by the fact that the lower emitter 320 andthe lower receiver 340 are open but the upper emitter 330 and the upperreceiver 350 were blocked in the previous state 600. This removal of thefirst product 190 is then completed in the present state 590 when bothpairs of emitters 320, 330 and the receivers 340, 350 are open. Themicro-controller 270 then sets the delay timer so as to permit the firstproduct 190 to be completely removed from the channel 140 and for thesecond product 200 to slide into place against the barrier 180 by theforce of gravity.

Likewise, in FIG. 7B a valid drop event is shown. The present state 590shows that the upper emitter 330 and the upper receiver 350 are blockedwhile the lower emitter 320 and the lower receiver 340 are opened. Inthe previous state 600, both pairs of the emitters 320, 330 and thereceivers 340, 350 are open. This means that the emitters 320, 330 andthe receivers 340, 350 were open in the previous state 600 becauseeither there was no first product 190 within the channel 140 or that thefirst product 190 was being inserted into the channel 140 and the secondproduct 200 was being pushed back towards the second end 170 of thechannel 140. In either case, the emitters 320, 330 and the receivers340, 350 were open. As the first product 190 is being placed within thechannel 140 in the present state 590, the upper emitter 330 and theupper receiver 350 are blocked while the lower emitter 320 and the lowerreceiver 340 are still open.

FIG. 8 shows an alternative scan routine to that found in FIG. 5, butwith the use of a lift/drop signature table 650 instead of the signatureanalysis sub-routine of FIG. 6. The signature table 650 provides thesame analysis as in the signature analysis sub-routine but in tableform. If the micro-controller 270 determines (1) that the delay timer isnot on, (2) that the upper emitter 330 and the upper receiver 350 wereopen in the previous state, (3) that the lower emitter 320 and the lowerreceiver 340 were open in the previous state, (4) that the upper emitter330 and the upper receiver 350 are closed in the present state, and (5)that the lower emitter 320 and the lower receiver 340 are closed in thepresent state, then a lift event has occurred. Likewise, if themicro-controller 270 determines that (1) the upper emitter 330 and theupper receiver 350 were closed in the previous state, (2) that the loweremitter 320 and the lower receiver 340 were open in the previous state,(3) that the upper emitter 330 and the upper receiver 350 are open inthe present state, and (4) that the lower emitter 320 and the lowerreceiver 340 are open in the present state, then a drop event hasoccurred.

Applying the use of the signature table 650 in FIG. 8, themicro-controller 270 checks the door switch 125 (if a door 120 is used),the hold switch 127, and selects the next product channel 140 at step660. At step 670, the micro-controller 270 reads the present state ofthe optical sensors 260. At step 680, the micro-controller 270 retrievesthe previous state of the optical sensors 260. At step 690, an eventsignature is created with the current state and the previous state ofthe optical sensors 260. At step 700, the signature table 650 iscompared with the event signature of step 690. At step 710, themicro-controller 270 determines whether a valid event has taken place,i.e., a lift or a drop. If so, at step 720, the micro-controller 270obtains the cooler identification number and the time stamp so as tocreate an event record. At step 730, the event record is stored in RAM277 or other type of memory device.

The event records may be accessed at any time. The event records may beorganized in a conventional spreadsheet format. FIG. 9 shows a samplespreadsheet layout 750. As is shown, the spreadsheet layout 750 includesthe cooler identification number 760, the channel number 770, the event780, i.e., either a lift or a drop, and the time stamp 790. A preferredspreadsheet 750 may be the Excel® spreadsheet software sold by theMicrosoft Corporation of Redmond, Wash. The data may be downloaded to astandard laptop computer, palmtop, or similar device via a serial portsuch as a RS232 port. Alternatively, the data may be transmitted viaradio frequencies, telephone, or other conventional means.

The present invention thus provides an accurate means for monitoring theinventory of a cooler or other type of product shelf. Further, thepresent invention also may provide consumer purchasing information inthat the nature of the products bought, the volume, and even the timethe products are bought may be available. This type of data may be usedto determine brand and packaging information and optimization.

A further embodiment of the present invention is shown in FIGS. 10-12.In this embodiment, the shelves 130 have a guard 800 positioned near thedoor 120 of the cooler 100. Specifically, the guard 800 is positionedalong the first end 160 of each channel 140 of the shelves 130. Theguard 800 may extend across all or some of the channels 140. The guard800 may be positioned directly in front of each of the posts 300, 310.The guard 800 preferably has a height that extends from about the floorof each channel 140 up to about each barrier 180. The guard 800preferably should have a size at least sufficient to cover the opticalsensors 260 on the posts 300, 310.

The guard 800 preferably may attach to the shelf 130 via a snap fit. Theguard 800 may have a first side 810 with a number of flanges 820 and anumber of extended lip areas 830 attached thereto or formed therein. Theflanges 820 may attach to a bottom tab 840 that extends from some or allof the channels 140 of the shelf 130. The extended lip 830 of the guard800 also may extend beyond the barrier 180 of each channel 140 and snapinto place thereto. The guard 800 also may be attached to the shelf 130by other types of conventional fastening means.

The guard 800 also may have a second side 850 with a plurality of panels860 thereon. The panels 860 each may accommodate an advertising indicia870 of various types. For example, the advertising indicia 870 mayinclude the name of the products 150 placed on the shelf 130. Any typeof graphics or advertisements may be used. The advertising indicia 870may be placed on a label 880 attached to each panel 860. The labels 880may be made from paper, plastic films, or similar materials.Alternatively, the advertising indicia 870 may be molded into the panels860 themselves. The advertising indicia 870 also may be attached to thepanel 860 by any other conventional means.

The guard 800 is preferably made out of PETG (Polyethylene TerepthalateGlycol) or similar types of thermoplastic materials. The guard 800 maybe made in an injection molding process as is well known to thoseskilled in the thermoplastic arts or other types of conventionalmanufacturing means. Further, other types of substantially rigidmaterials may be used such as wood, metals, glass, and other types ofconventional materials.

The guard 800 is preferably formed to follow the contours of the barrier180 and hence the products 150 positioned in each of the channels 140.The guard 800 may be, but not necessarily, made out of a substantiallyopaque material or a material colored an opaque shade. Alternatively,the label 880 for the advertising indicia 870 may be substantiallyopaque such that light does not diffuse through both the label 880 andthe guard 800. In the example herein, the PETG material is notparticularly opaque. The label 880 with the advertising indicia 870thereon is sufficiently light dampening such that the operation of theoptical sensors 260 on the posts 300, 310 is not interfered with orinterrupted. In sum, the guard 800 may be made of an opaque material,may be colored a light dampening color, or the guard 800 may use a label880 that substantially prevents diffusion of light therethrough.

The guard 800 may positioned in front of the posts 300, 310 so as toprevent exterior light from interfering with the operation of theoptical sensors 260 positioned thereon. The exterior light may beambient light from outside the cooler 100 or one or more light sourcesmay be positioned within the cooler 100. The guard 800 with the panels860 thereon also may be used without the cooler inventory system asdescribed herein simply for its ability to provide a visible locationfor the advertising indicia 870.

FIG. 13 shows a further alternative embodiment to the guard 800. In thisembodiment, a wing 890 is positioned adjacent to each optical sensor260. The wings 890 may be attached to the posts 300, 310 by conventionalmeans. The wings 890 are positioned on the posts 300, 310 so as to blocklight from directly reaching the optical sensors 260. The wings 890 maybe of any convenient size sufficient to cover the optical sensor 260.The wings 890 may be made out of the same thermoplastic material asdescribed above or any other type of substantially rigid, substantiallyopaque material. Likewise, the wings 890 may be made out of a non-opaquematerial and covered with a light dampening material. Any combination ofthe guard 800, the guard panels 860, and the wings 890 may be used.

It should be apparent that the foregoing relates only to the preferredembodiments of the present invention and that numerous changes andmodifications may be made herein without departing from the spirit andscope of the invention as defined by the following claims.

We claim:
 1. An apparatus for tracking the movement of a plurality ofproducts, comprising: a shelf; said plurality of products positioned onsaid shelf; an optical sensor positioned about said shelf so as to trackthe movement of one of said plurality of products; and a guardpositioned about said shelf adjacent to said optical sensor so as toprevent exterior light from interfering with said optical sensor.
 2. Theapparatus of claim 1, wherein said guard extends across said shelf. 3.The apparatus of claim 1, wherein said guard comprises a plurality offlanges so as to attach to said shelf.
 4. The apparatus of claim 1,wherein said guard comprises an extended lip so as to attach to saidshelf.
 5. The apparatus of claim 1, wherein said guard comprises aplurality of panels thereon.
 6. The apparatus of claim 1, wherein saidguard comprises a thermoplastic.
 7. The apparatus of claim 1, whereinsaid guard comprises Polyethylene Terepthalate Glycol.
 8. The apparatusof claim 1, wherein said guard comprises a substantially opaquematerial.
 9. The apparatus of claim 1, wherein said guard comprises awing positioned adjacent to said optical sensor, said wing sized so asto prevent exterior light from interfering with said optical sensor. 10.The apparatus of claim 1, wherein said optical sensor comprises acontroller so as to track the removal of one of said plurality ofproducts from said shelf and to track the insertion of one of saidplurality of products into said shelf.
 11. The apparatus of claim 1,wherein said exterior light comprises ambient light.
 12. The apparatusof claim 1, wherein said exterior light comprises a light sourcepositioned within said cooler.
 13. The apparatus of claim 1, whereinsaid shelf comprises a first end and wherein said optical sensor andsaid guard are positioned about said first end.
 14. The apparatus ofclaim 1, wherein said guard comprises advertising indicia thereon. 15.The apparatus of claim 14, wherein said advertising indicia comprises alabel.
 16. The apparatus of claim 1, wherein said guard comprises atranslucent material and a covering layer.
 17. The apparatus of claim16, wherein said covering layer comprises a substantially opaquematerial.
 18. The apparatus of claim 1, wherein said optical sensorcomprises one or more emitters and one or more receivers.
 19. Theapparatus of claim 18, wherein said one or more emitters and one or morereceivers comprise a pair of emitters and receivers positioned along adiagonal line.
 20. An apparatus for tracking the movement of a pluralityof products, comprising: a shelf; said plurality of products positionedon said shelf; said shelf comprising a first end; an optical sensorpositioned about said first end of said shelf; a guard positioned aboutsaid first end of said shelf adjacent to said optical sensor; and acontroller functionally connected to said optical sensor so as to trackthe removal of one of said plurality of products from said first end ofsaid shelf and to track the insertion of one of said plurality ofproducts into said first end of said shelf.
 21. An apparatus fortracking the movement of a plurality of products, comprising: a shelf;said plurality of products positioned on said shelf; an optical sensorpositioned about said shelf so as to track the movement of one of saidplurality of products; and a guard positioned about said shelf adjacentto said optical sensor; said guard comprising adverb sing indiciathereon.